The Boston Newspaper Guild is the biggest union at the Globe, and the union that's currently being asked by the NYT Co. to make the biggest sacrifices to prevent the paper from closing. As such, it's poised to help shape the future of Boston journalism, for better or worse. But only one member of the Guild's seven-member executive committee--Kathy McCabe, the union's recording secretary, who's a correspondent for the Globe North section--actually works as a journalist.